Differential Problems HELP

I need help on the following problems. I am not sure how to even start number 5. Will you please check over my work. The questions and my work are attached in a word document, I tried copying it but the equations did not copy. Any help will be greatly appreciated.

First, many people will not even open a Word file for fear of viruses. It's not THAT difficult to type your problems in! You don't even know how to start number 5?
Calculate the actual value of P given in number 2. The calculate the actual value of P after making the changes given in number 3. Subtract!